This disclosure relates to automatic transmission control for vehicles such as automobiles, trucks, etc. Specifically, the disclosure relates to the control of solenoids used to control hydraulic pressure associated with clutches for disengaging and engaging of automatic transmission gears.
Many present automatic transmissions use linear solenoids to vary the hydraulic pressure delivered to each clutch of an automatic transmission system. The solenoids have an inherent tolerance range for the amount of hydraulic pressure delivered vs. electrical current supplied to the solenoid. In other words, the amount of hydraulic pressure provided by two or more solenoids can vary for a given amount of solenoid input current. Consequently, the automatic transmission shifting algorithm parameters require calibration to account for the tolerance ranges of the solenoids.
One approach for calibrating an automatic transmission solenoid is disclosed in U.S. Patent Publication No. 2004/0206155. This publication discloses a method of calibrating a solenoid by sweeping the solenoid with increasing current from a minimum to a maximum. The hydraulic pressure output and corresponding solenoid current are recorded at preselected increments. The calibration data is stored in an electronic device and accessed by a controller to control the solenoids during execution of automatic transmission shifting algorithms.
Other present automatic transmission solenoid calibration techniques include closed loop systems to control shifting clutch actuators such as a solenoid. For example, U.S. Patent Publication 2004/0122577 discloses a closed loop control system for shifting clutch actuators.
This disclosure provides a system and method of operating and testing automatic transmission solenoids within the performance specifications of the solenoids.